Smart　surfaces　with　responsive　wettability　are　unstable,　and　depend　upon　continuous　external　stimuli,　which　limits　their　widespread　application　in　switchable　oil/water　emulsions　separations.　In　this　study,　a　Ti-based　3D　porous　structure　(SLM-3DTi)　is　printed　using　advanced　selective　laser　melting　(SLM)　technology　for　the　switchable　separation　of　oil/water　emulsion.　With　the　assistance　of　the　computer　program,　porous　structure　and　re-entrant　texture　can　be　easily　designed　and　printed　in　one　step.　Without　any　continuous　external　stimulus,　the　wettability　of　SLM-3DTi　can　be　reversibly　switched　between　underwater　superoleophobicity　and　underoil　superhydrophobicity　simply　by　drying　and　washing　cycles.　The　SLM-3DTi　achieves　switchable　surfactant-stabilized　oil-in-water　emulsion　(SSE(o/w))　and　surfactants-stabilized　water-in-oil　emulsion　(SSE(w/o))　separation　with　purity　above　99.8%　at　a　flux　of　more　than　2000　L m−2 h−1.　In　addition,　the　re-entrant　texture　of　the　SLM-3DTi　surface　is　formed　with　the　partially　melting　powder　particles　on　the　part　contour,　which　has　much　stronger　mechanical　durability　than　any　binder.　Furthermore,　SLM-3DTi　has　excellent　corrosion　resistance　due　to　the　material　properties　of　Ti.　More　importantly,　based　on　the　visualization　analysis　of　the　simulation,　the　mechanism　of　SLM-3DTi　emulsion　separation　is　further　elucidated.　Therefore,　SLM-3DTi　has　broad　practical　application　potential　for　high-flux,　high-purity,　and　switchable　oil/water　emulsion　separation.　©　2023　Wiley-VCH　GmbH.